1. Field of the Invention
The present invention relates to a production process of a hexagonal honeycomb structure used as a catalyst support and so forth in, for example, an automobile emission purification device.
2. Description of the Related Art
Honeycomb structures made of ceramics having for their main component, for example, cordierite are widely used, for example, as a support for automobile emission purification catalysts. In recent years, the partition thickness of the honeycomb structure has been made thinner to reduce the thermal capacity of the support for the purpose of improving the emission purification performance. In order to maintain the durability of the overall honeycomb structure when reducing partition thickness, it is advantageous to make the cells that compose the honeycomb form hexagonal. Consequently, as shown in FIG. 2 to be described later, development of a hexagonal honeycomb structure 8 in which the shape of cells 80 and partitions 81 is hexagonal has been proceeding.
This hexagonal honeycomb structure can be produced by extrusion molding mixed raw materials using an extruder followed by drying and baking in the same manner as the case of a conventional square honeycomb structure.
However, the production process of the above-mentioned hexagonal honeycomb structure of the prior art has the problems described below.
Namely, in the case of performing each of the above-mentioned production steps of extrusion molding, drying and baking in the state in which the lengthwise direction of the honeycomb structure is in the horizontal direction as has been done in the past, cell deformation in the case of a hexagonal shape is greater than in the case of a square shape. Consequently, the overall dimensional accuracy of the hexagonal honeycomb structure is decreased.
In consideration of the above-mentioned problems of the prior art, the object of the present invention is to provide a production process of a hexagonal honeycomb structure offering low deformation of the hexagonal cells.